3rd party shortcut f5 works on some machines and in firefox, not i

Please help. f5 in this app works in firefox, it works on some machines but
not others.
More details. We use a web based / iis library system called Oliver
developed by Softlink. the circulation desk allows the use of some
shortcuts/programmed function keys. F2 will bring up borrower details ok, f4
will bring up loan information ok, etc. f5 and ctrl f5 SHOULD bring up a
search pop out window, but nothing happens. (it does not refresh the window
either, which we dont want anyway, but i included that information for
completeness )

It works ok on most collegues machines and it will work if i use Firefox.
I have looked at any possible differences between working machines and my
own, as far as internet explorer updates and i dont have anything updatewise
they dont have.
I have disabled and one by one reenabled browser addons, activex's, I have
removed/disabled pop up blockers, i have even almost completely removed all
security settings but to no avail.

I'm thinking of some kind registry setting or something needs adding or
changing?, but thats a bit out of my league. the problem is present in ie6
and seven. ie8 beta won't completely run the application (reports wont run)

Its bit of a cop out to completley removed ie and reinstall it. there must
be something small that is doing it. there are multiple users with this
problem, please help.
All ideas gratefully accepted!

note: to replicate the problem, we created a shortcut to any application,
and set a shortcut key as CTRL + f5.
then we deleted that shortcut and the assigned shortcut in our oliver App
went with it. ctrl and f5 would no longer work. to get it back we used
ccleaner and was ok again. unfortunately that didnt work on machine which
already had the problem.

yes the support staff are aware of the issue but its a bit of a head
scratcher.

Thanks for any help or suggestions.

Rob